The invention relates to a device for discharging a pasty two-component mixture, e.g. a mixture of a dental impression substance and a catalyst for initiating or accelerating the hardening.
For applying multi-component substances in mixed form, discharge devices are known which comprise a supply container with at least two chambers for respectively one of the pasty components of the mixture. Assigned to each chamber is an outlet stub for discharging the pasty substance upon application of pressure. To allow discharge of the pasty substances in mixed form, the outlet stubs of the known devices have a mixer unit mounted thereon, comprising a mixer housing including a substantially tubular portion and a coupling end for attachment to a supply container. In the tubular portion of the mixer housing, a mixer element is arranged by which the components, which have been supplied via separate channels, are subjected to a turbulence and mixing effect. Said channels are formed in the coupling end of the mixer housing and extend from the inlet stub of the coupling end to the mixer element. A device of this type is known e.g. from EP-A-0 730 913.
Depending on the composition of the pasty components, their mixing will result in the respectively desired chemical reactions. For instance, if one of the two pasty components is a dental impression substance, the adding of a second component initiates and accelerates the polymerisation of this impression substance. Should this second component (also referred to as a catalyst) penetrate, via the mixer unit, from the one chamber into the other chamber of the supply container or should already the outlet stub of the chamber for the dental impression substance by contaminated with the catalyst, the whole device will be rendered useless, which, depending on the extent to which the chambers are filled, will cause a considerable loss of expensive material. Therefore, the two component flows have to remain separated from each other for the longest possible stretch of their moving paths and be brought together only within the tubular portion of the mixer housing.
In the known discharge device for pasty two-component mixtures, the mixer housing is detachably locked to the supply container by means of a holding shell. The holding shell is supported for rotation on the mixer housing and is provided with radially outward locking projections formed in the manner of bayonet locks, which can be rotated to move under corresponding grip-over projections of the supply container.
The invention further relates to a device for opening a tube bag containing a pasty substance. Said device is further provided to guide the pasty substance out of the tube bag.
The pasty substances are offered in rigid containers or cartridges with displaceable bottom walls which are advanced by plunger elements arranged to be advanced by hand or by means of an engine in order to exert pressure on the pasty substances, thus discharging the substances from the cartridges and the cartridges or containers. In recent years, for reducing the packing material, the pasty substances have been increasingly offered in tube bags. For discharging the pasty substances, the tube bags have to be opened, preferably on their end sides. This is preferably performed by means of stationary piercing mandrels or the like cutting elements arranged on the end wall of a holding cap surrounding the end side of the tube bag and comprising a discharge stub. From EP-A-0 787 655, it is known to provide the inner projection of the holding cap with a piercing tube resiliently biased in the direction of the end face of the end of the tube bag. The as of yet known systems for automatic opening of tube bags are in need of improvement in so far as, for opening the tube bag, it is always required to exert pressure onto the tube bag and thus also on the pasty substance in the tube bag. Thus, the process of opening the tube bag is accompanied by the discharge of the pasty substance.
As already mentioned above, discharge devices are used intermittently, the period between two successive uses being possibly so long that the mixture in the mixer unit will harden. As a result, the mixer unit has to be removed and replaced by a new one before the discharge of a mixed substance can be continued. Thus, the mixer unit is a disposable component, making it desirable to keep the number of components of this disposable mixer unit as low as possible.
It is an object of the invention to provide a device for the discharge of a pasty two-component mixture, comprising a mixer unit with a reduced number of parts.
According to the invention, to achieve the above object, there is proposed a device for the discharge of a pasty two-component mixture comprising:
a supply container with two chambers for respectively one pasty component of the mixture, the supply container being provided with a respective outlet stub for each chamber,
a mixer unit comprising a tubular mixer housing with a mixer element arranged therein, the mixer housing comprising a coupling end to be coupled to the supply container and having a two inlet stubs and two channels for the pasty components of the mixture leading to the mixer element, and comprising, on its opposite end, an outlet opening for the mixture, the inlet stubs being adapted for insertion into the outlet stubs or vice versa, and
a holding shell for the coupling end of the mixer housing arranged for rotation on the supply container, the holding shell surrounding the two outlet stubs and comprising a recess of a shape at least in parts substantially identical with the cross sectional shape of the coupling end of the mixer housing, the holding shell being rotatable between a receiving rotational position in which the recess is oriented corresponding to the orientation of the coupling end of the mixer housing in the state where the inlet stubs are connected to the outlet stubs of the supply container, and
a locking rotational position in which at least a part of the recess edge of the holding shell is in engagement over parts of the coupling end of the mixer housing.
In the inventive discharge device, the holding shell holding the mixer unit is arranged not on the mixer housing but on the supply container. On this supply container, the holding shell is supported for rotation about its longitudinal axis. The holding shell surrounds the two outlet stubs of the supply container and is provided, on its front end facing away from the supply container, with a recess which in the first rotational position of the holding shell (receiving rotational position) allows the mixer housing to be mounted onto the outlet stubs of the supply container, while, in a second rotational position (locking rotational position) the edge of the holding shell delimiting the recess has been moved over partial regions of the coupling end, e.g. over radially projecting flange portions of the coupling end of the mixer housing, thus locking the mixer housing to the supply container. Therefore, the holding shell is not a component of the mixer unit anymore and thus will be preserved for the whole period during which the discharge device is used for application of the two-component mixture.
In an advantageous embodiment of the invention, the coupling end is provided with two diametrically opposite and radially extending projections, while the holding shell is formed with a recess of a shape identical with the cross sectional shape of the coupling end at the level of the projections of the latter. Particularly, the coupling end of the mixer housing is of a substantially oval shape in the region of the radial projections. The recess of the holding shell, when in its receiving rotational position, is arranged relative to the outlet stubs of the supply container in the same manner as the inlet stubs of the mixer housing relative to the outer projections. Thus, the coupling end of the mixer housing can be moved through the recess of the holding shell until the inlet stubs of the mixer housing have been received by the outlet stubs of the supply container, or vice versa. In this position, the recess edge of the holding shell is arranged above the outer projections on the coupling end of the mixer housing so that, by rotating the holding shell into the locking rotational position, regions of the recess edge engage the outer projection from above. Suitably, the holding shell is in both of these rotational positions secured against unintended further rotation or reverse rotation, which is preferably accomplished by a corresponding locking effect. For the handling of the holding shell, it is further suitable to allow rotation of the holding shell only between its receiving rotational position and its locking rotational position. In this regard, it would be convenient to realize the limitation of the rotational movement by corresponding stopper elements on the holding shell and the supply container.
For this purpose, the invention proposes a device for opening a tube bag containing a pasty substance, which device does not necessarily have to be realized in combination with the above described mixer holding device although such a combination is preferable, and which comprises
a receiving cap for receiving an end side of the tube bag, which end side comprises an end face, the receiving cap comprising an end wall forming an abutment plane for the end face of the tube bag, and an edge extending from the end wall,
an opening formed in the end wall and surrounded by a stub projecting from the end wall, and
a piercing tube guided in the stub for axial displacement.
In this device, it is provided according to the invention that the piercing tube is manually displaceable from a retracted position in which the piercing tube does not extend beyond the abutment plane into an advanced position in which in the piercing tube extends beyond the abutment plane.
The inventive device is provided with a piercing tube which is guided to be axially displaced in the discharge stub of a receiving cap. In the opened state of the tube bag, the pasty substance will be discharged through this stub to be applied directly, or, in case of a two-component material, to be mixed with another component of the pasty substance. The discharge stub is arranged to radially project from the end wall of the receiving cap, with a continuously surrounding edge projecting from the end wall in a direction opposite to the discharge stub. Thus, the receiving cap surrounds one of the two end sides of the tube bag whose end face abuts the end wall of the receiving cap on an abutment face formed by the latter. The piercing tube of the inventive device is manually displaceable from a retracted position to an advanced position. This displacement can be performed either directly by hand in that the piercing tube is manually shifted within the stub, or indirectly by manually moving an operating element which in turn via an abutment face is in abutment on the piercing tube and thus, when being moved itself, will pull along the piercing tube. In both cases, the piercing tube can be displaced from the retracted position in which it does not protrude beyond the abutment plane of the receiving cap, formed by the end wall, into the advanced position in which is projects beyond the abutment plane and thus, with the receiving cap receiving the tube bag, is immersed into the end face of the latter and opens the tube bag. The piercing tube can be arranged in the stub ex factory and will thus be located in its retracted position. By way of alternative thereto, it can be provided that the piercing tube is inserted into the stub by the user. In both cases, it is suitable if the piercing tube in its retracted position is secured against unintended movement from its retracted position by a locking effect or the like. This is advantageous to the user to whom, under the tactile aspect, the retracted position will be perceivable as a defined position of the piercing tube.
The advantage of the inventive opening device resides in that the process of opening the tube bag is separated from the process of discharging the pasty substance from the tube bag. Thus, the tube bag will not be subjected to an increased pressure when being opened, preventing an undesired escape of pasty substance from the tube bag when the latter is being opened. This facilitates the handling of the tube bags.
The inventive device is useful both for receiving caps for a single tube bags and for combined receiving caps for a plurality of tube bags, e.g. two tube bags. In the latter case, the receiving cap comprises a plurality of discharge stubs respectively provided with one piercing tube. These piercing tubes can be connected to each other to be driven in common into the respective tube bags. Of course, it can also be provided that the piercing tubes are not connected to each other so that each tube bag can be xe2x80x9ctappedxe2x80x9d separately.
It is particularly convenient if the piercing tube in its retracted position projects beyond the discharge end facing away from the end wall of the receiving cap. Notably, in this case, the axial displacement of the piercing tube can be effected by a mere movement into the stub. Once the piercing tube has been completely moved into the stub, the advanced position has been reached and the piercing tube has been driven into the tube bag.
Suitably, it is provided that the piercing tube in its advanced position is secured against undesired return movement in the direction of the retracted position, and in its retracted position is secured against undesired movements into the advanced position. As already mentioned above, this can be realized by locking the piercing tube in or on the stub. As an alternative thereto, the piercing tube, which in its retracted position projects from the discharge end of the stub, can be protected by a removable protective cap which can be pushed over the stub and fixed to the stub. This protective cap serves for protection during shipment and, prior to insertion of the piercing tube, is removed, e.g. unscrewed, in order to expose the piercing tube. An alternative to the protective cap resides in a spacer arranged between the end of the piercing tube projecting from the stub, and the discharge end of the stub. Particularly, this spacer is formed as a resilient clip surrounding the piercing tube. This resilient clip can be laterally withdrawn from the piercing tube so that the latter can then be axially displaced. The spacer is supported between an outer projection on the piercing tube and the discharge end of the stub.
If the piercing tube is moved not directly manually but indirectly manually via an operating element, this operating element can be utilized as a safety means for protecting the piercing tube from undesired movements from the retracted position into the advanced position. The operating element is suitably provided in the manner of a shell element arranged on the stub and displaceable axially along the stub. This shell element can be locked, in two axial positions corresponding to the retracted position and the advanced position of the piercing tube, to the stub and respectively the receiving cap against undesired axial movements. Advantageously, the shell element is formed as a screw element comprising an inner thread portion adapted for engagement with an outer thread portion on the stub. By means of these threaded portions, the shell element can be axially displaced for driving the piercing tube into the tube bag. Both the shell element and the stub are provided, on both sides of their threaded portions, with regions which are free of threads. As long as the two threaded portions are not in threaded engagement with each other, a rotation of the shell element will not lead to an axial displacement. Besides, the threaded portions, while not in mutual threaded engagement, preclude a linear axial displacement of the shell element. Thus, the latter is secured against undesired axial movements before and after the threaded engagement of the two threaded portions.
Embodiments of the invention will be described in greater detail hereunder with reference to the Figures.